Radiofrequency power transmitters usually comprise power stages involving tubes using one or more high DC voltages. These DC voltages are generally provided by HV power supplies on the basis of an AC electrical supply network. For power transmitters the power supply networks are three-phase networks of frequency 50 Hz, or 400 Hz notably in the case of onboard equipment.
The high-voltage power supplies of the state of the art are achieved according to a structure calling upon a cascade of at least three energy conversion stages, namely a three-phase rectifier bridge for the network current, of Graetz type, (rectification by diodes) followed by a buffer stage converting the rectified voltage emanating from the Graetz bridge into current or voltage, and then a stage generating the high DC voltage or voltages for end use.
The typical efficiency of such a type of power supply is of the order of 85%.
The major disadvantage of this type of power supply with three stages in cascade is of drawing current from the network with a high distortion rate, thus degrading the power factor of the supply. The power factor Fp is defined by the relationFp=Pact/(Ueff·Ieff)                Pact is the active power provided by the network to the power supply,        Ueff the effective voltage of the network, and        Ieff the effective current absorbed by the power supply        In the best case the power factor is equal to 1.        
These distortions of the network current may be corrected by an external sub-assembly coupled to the input of the power supply and called the power factor corrector. Nonetheless, power factor correctors exhibit the disadvantage of decreasing the reliability of the power supply with a significant impact on its cost, its volume and its mass.
The use of a power factor corrector leads, furthermore, to a decrease in the overall efficiency of the power supply, which is not acceptable for onboard equipment.